This document deals with mobility for a moving network, which is defined as a network that is movable in relation to its home network. A moving network can change its point of attachment to a fixed infrastructure or it may have many points of attachment to a fixed infrastructure, but it is still able to communicate with a home network through a mobile router having access to an external access through which all communication nodes in the moving network can communicate. Such a communication node in a moving network is called a moving network node. In the case of a moving network on e.g. an airplane, the moving network will comprise communication nodes, which may be different users' communication devices, such as laptops, mobile phones, PDAs (Personal Digital Assistants) etc., which communication nodes communicate wireless or wireline with a mobile router within the airplane, such that all communication destined to an external address will pass via the mobile router. A moving network may also be e.g. a Personal Area Network (PAN), wherein a PAN comprises all communication devices belonging to a user and situated within short range radio communication distance from each other. In this document, each node in the moving network or connected to the moving network that works like a router for data originating from a moving network node and destined to an address external of the moving network is defined as a mobile router. Examples of such mobile routers are: a PAN device working as a router in a PAN, and a router in a moving network on a vehicle. Note that a node may have both roles, i.e. being both a moving network node and a mobile router, for example a PAN device such as a mobile phone in a PAN.
“The Network Mobility (NEMO) Basic Support Protocol”, by Devarapalli et al, published January 2005 as a Request For Comments 3963 by the Internet Engineering Task Force, identifies a protocol that enables a moving network to attach to different points in the Internet. The protocol is an extension of Mobile IPv6, and allows session continuity for every communication node (or communication device) in the moving network as the moving network moves. It allows a mobile router to maintain a stable network address prefix for a moving network, even as the mobile router changes its, and thus the moving network's, point of attachment to a fixed network infrastructure. This prefix stability is achieved through a solution similar to the mobile IPv6 solution, i.e. by making a home agent (HA) in the home network of the mobile router a fixed point of attachment for the Mobile Router (MR) and maintaining connectivity between the HA and the MR through a tunnel. The address prefix, which is called Mobile network prefix (MNP) in the NEMO protocol, is allocated from the address range of the home network, and can thus remain the same even as the MR and its network move. When the MR attaches to a network in a new location, it acquires a new care-of address in the new network, which care-of address is used to locate the MR in the new network, but its home address and address prefix are unchanged. However, just like in Mobile IPv6 the MR has to register its new care-of address in the HA in order to maintain the tunnel between the Mobile Router and the Home Agent.
If, in the current NEMO solution, a bad tunnel is experienced, it will be replaced by a new tunnel by performing a new registration with the HA, this time with a different care-of address, unless the tunnel is re-established through the same interface and point of attachment, and possibly configured on a different interface, depending on the nature of the tunnel problems. If a communication node could get Internet access through multiple access media simultaneously, i.e. the moving network could have multiple tunnels established simultaneously, a data flow could be moved from a bad tunnel to a good tunnel much quicker than if only one tunnel at a time can be established. Also, for matters of cost, bandwidth, delay etc. it could be useful for a communication node to get Internet access through multiple simultaneous tunnels. However, the NEMO basic support protocol does not allow this because it allows only a single care-of address to be registered in the Home Agent (HA) for a certain Mobile Router (MR) at any one time. Multiple simultaneous care-of addresses are not allowed and thus multiple simultaneous accesses and MR-HA tunnels are not possible for a MR.
Although, such a procedure for managing different external access resources simultaneously accessible by a mobile router in a moving network is suggested in the co-pending patent application PCT/SE2004/001578 by the same applicant. For this reason, a tunnel is set up over each of the different external access resources available from the mobile router such that the external accesses are simultaneously accessible. To be able to fully make use of the different external access resources, this procedure suggests that the mobile router controls the use of the different external access resources for data packets sent between the mobile router and the home agent of the mobile router. To achieve this, the mobile router classifies a data packet based on information in the packet and selects an access resource for sending the packet based on the classification and on information of the different external access resources.
The procedure described above only discusses a moving network having one mobile router with a plurality of external access possibilities. Although, it may happen that all external accesses present in an area are not handled by one and the same mobile router. For example, on a train there may be a fixed mobile router mounted in each railway-carriage. Also, for technical reasons, different external accesses may not be handled by the same mobile router. Therefore, to be able to give the moving network nodes in a moving network the ability to use all external accesses that are present in an area, a procedure for managing different external access resources simultaneously accessible by more than one mobile router in a moving network is suggested in the co-pending patent application PCT/SE2004/001994 by the same applicant.
In the procedure described in PCT/2004/001994, the more than one mobile routers forward traffic between each other so that the correct access is used independently of how the mobile network nodes behave. In this procedure, the same mobile network prefix (MNP), i.e. address prefix, is used by all mobile routers in the moving network. This is the case for example when the mobile routers have the same home network, e.g. same home agent in the same home network.
Although, in some cases it may happen that the moving network has multiple MRs but they are unsynchronized with regards to address prefix management. This means that an MR may be assigned an address prefix or MNP different from what another MR in the same moving network is using. The MRs may connect to the same or to different HAs. The MRs are assigned different address prefixes from their HAs and they advertise them into the moving network. Although, it is still of interest to be able to use all external access of the moving network for all MNNs. The focus of the solution is to let the MRs perform external access selection for the flows of the MNNs in the most flexible manner. Therefore, it would be desirable if it would be possible to use any of the external accesses accessible from any of the MRs for routing data packets originating from any of the MNNs to a home agent of the moving network, also in the case where the MRs in the moving network are unsynchronized with regards to prefix management (e.g. they are allocated different prefixes).
The term flow or data flow used in the application is a loose term for a connection between two end nodes. A flow between a first and a second end node may have two directions: from the first node to the second node and vice versa. Thus, in the application, a data flow comprises an uplink part and a downlink part, wherein the uplink part is in the direction from the moving network node to the home agent (and further to the correspondent node), and the downlink part is in the direction from the home agent to the moving network node. A TCP (Transmission Control Protocol) connection is typically seen as a flow. A node can have multiple flows towards different correspondent nodes and also multiple flows towards the same correspondent node. Each flow comprises data packets. A flow is typically defined by the source and destination IP addresses and port numbers, plus the transport protocol in use, such as TCP or UDP (User Datagram Protocol). It is also possible to instead define a flow by its flow label (in IPv6) or its SPI (Security Parameter Index) together with the source and destination IP addresses, and the protocol in case of the SPI. The flow label is more specific than the port numbers and should have precedence over them. The SPI is used in IPsec (IP security as defined in RFC 2401 “Security Architecture for the Internet Protocol”), together with the destination IP address and the protocol to identify the security association, and the SPI-destination address-protocol triplet is typically used as a (unidirectional) flow identifier when the packet is encrypted and the port numbers are visible only to the receiving end-node.
The term external access or link defines one possible way of getting external access from the moving network. Each external access does not have to be of different types, although this is the most natural case. It may be possible that two external accesses are of the same type but differ in terms of e.g. current load or operator. There is one (primary) tunnel established between a Mobile Router and a Home Agent per external access.
The term Home Agent used in the application should be interpreted as any node in a home network working like a mobile anchor point to the moving network, i.e. facilitating communication from the moving network over an external network and the home network, such that the present invention can be used.